The present invention is related to thermal control systems generally, and more particularly to fins for dissipating heat.
Heat pipes are widely used to transfer heat with a very small temperature drop (xcex94T) between the evaporator (which receives heat) and the condenser (which rejects heat to a heat sink or to the surroundings). A heat pipe is a sealed tube or envelope containing a working fluid that is a phase change material. One end of the heat pipe, called the evaporator, receives heat from a heat source. The working fluid in the evaporator vaporizes, absorbing energy as the latent heat of vaporization. At the condenser end, the heat is removed, and the vapor returns to the liquid state. The liquid is returned to the evaporator, by capillary action or by gravity, depending on the application and the configuration of the heat pipe.
Fins are widely used for dissipating heat from components that produce heat, including electronics and fossil fuel engines. Fins are the major component of most heat sinks. Fins provide extended surfaces to increase convection heat transfer. In general, a heated surface within a fluid can reject heat by convection at a rate proportional to its surface area. Fins can greatly increase the surface area of an object, particularly when a large number of parallel fins are located in a small volume. It is common to place a plurality of fins on the condenser of a heat pipe, so that a greater amount of heat can be removed from the condenser, and hence, from the heat source with a given xcex94T.
Heat pipes typically have a round cross section. Fins may be extruded, stamped, die cast, or folded for use as an extended heat transfer surface. Fins are applied to the exterior of the condenser, for example, by brazing.
U.S. Pat. No. 6,234,210 B1 describes a heat pipe having an elliptical cross-section. Heat exchange fins are mounted to the heat pipe at the condenser end. The fins are galvanized on the heat pipe. Spacer pins are used to support and space the heat exchange fins from each other.
An improved fin and an improved heat pipe and fin assembly are desired.
One aspect of the invention is a fin comprising a plate. The plate has a hole therethrough. The hole has two elongated flat sides and two curved portions connecting the flat sides. The elongated sides have a length that is substantially greater than a radius of curvature of the curved portions. The plate has at least one collar portion adjacent to the hole. The collar portion extends approximately in a direction normal to the plate.
Another aspect of the invention is a heat pipe assembly, comprising: a heat pipe and at least one fin. The heat pipe has an envelope. The envelope has two elongated flat sides and two curved portions connecting the flat sides. The elongated sides have a length that is substantially greater than a radius of curvature of the curved portions. The at least one fin comprises a plate. The plate has a hole therethrough that is sized to accommodate the envelope of the heat pipe. The hole has two elongated flat sides and two curved portions connecting the flat sides. The elongated sides have a length that is substantially greater than a radius of curvature of the curved portions. The plate has at least one collar portion adjacent to the hole. The collar portion extends approximately in a direction normal to the plate.
Still another aspect of the invention is a method for making a heat pipe assembly, comprising: providing a heat pipe having an envelope, the envelope having two elongated flat sides and two curved portions connecting the flat sides, the elongated sides having a length that is substantially greater than a radius of curvature of the curved portions; forming a fin having a hole therethrough sized and shaped so as to accommodate the envelope; and placing the fin on the envelope.